A "Call for Civil Discourse" in a political context is a rhetorical trick. For that matter, a "call for civil discourse" might itself be a snide partisan jab…depending on the context.
A "call for civil discourse" leveled at one's partisan opponents is an overt accusation that the opponent is uncivil.
At its worst, "calls for civil discourse" can have the negative effect of cutting large segments of the population out of the system.
False claims to civility and charges of incivility were at the heart of the mistreatment of Native Americans in the West and blacks in the Jim Crow South. One simply framed these groups as uncivil dullards, then systematically dismissed legitimate grievances.
False calls for civil discourse are most damaging in an image driven society in which many confuse civility with tone. In such societies the ruling class can get away with all sorts of horrific actions. Historically, one finds that many of the worst atrocities were committed by people who could maintain an even tone while doing wrong.
Overall, a discussion of how we should engage in civil discourse is a good thing. When done correctly, civil discourse will give voice to more people in society and will even lead to a higher quality of discourse.
It is, after all, high quality discourse that we should aspire to. High quality discourse is that which allows the voices of many and brings the best ideas to surface.
That said, whenever one hears a call for "civil discourse," one should look at context of the call. If the call is aimed at one's opponent or if it cuts voices out of the conversation, then the person or group making the call might, in actuality, be the worst rogue in the room.